Security issue in IE7?

We received reports this morning that a security researcher had found a bug in the IE7 Beta 2 Preview release. This issue reportedly crashes IE and is exploitable to execute arbitrary code on the user’s computer. Naturally, we take the security of IE and our users’ safety very seriously, so we investigated immediately. We did confirm that the bug crashes IE. However, we did not find that the bug was exploitable by default to elevate privilege and run arbitrary code.

This bug had already been found during our code review and analysis that is a mandatory part of our development process; it was scheduled to be fixed before our next public release. We do not believe this bug is easily exploitable, and as an extra defense, the /GS flag also catches the overrun. This is a compiler flag that tells Windows to watch for some classes of buffer overflows. If Windows sees a problem, it kills the application, in this case IE, instead of running the exploit code. While this is certainly not our primary line of protection, it does offer defense-in-depth to help keep our customers secure.

At this time, we are not aware of any active exploits taking advantage of this bug. We will continue to monitor the situation and evaluate our response.

Finally, I’d like to reiterate the importance of the responsible disclosure of security issues. We firmly believe that privately disclosing security issues to software vendors is the best way to keep the users of the world secure. To report a security issue against any Microsoft product, please contact secure@microsoft.com. For other feedback on IE7, please use the methods Jason mentioned yesterday.